Borate fluorescent powder and preparing method thereof

ABSTRACT

A borate fluorescent powder and a preparing method thereof are provided. The formula of the borate fluorescent powder is Ba2-nSrnLu5-x-y-m-zLmCexTbyEuzB5O17. L is one or any combination of the elements Gd, La, and Sc. Ranges of x, y, z, m, and n are respectively 0&lt;x≤0.6, 0&lt;y≤3, 0&lt;z≤0.4, 0≤m≤1, and 0≤n≤0.5. The borate fluorescent powder provided has a stable crystalline phase, high luminous efficiency, and decent thermal stability, and can be applied to ultraviolet LEDs or near-ultraviolet LEDs to construct white LEDs.

RELATED APPLICATIONS

This application is a National Phase of PCT Patent Application No.PCT/CN2018/113306 having International filing date of Nov. 1, 2018,which claims the benefit of priority of Chinese Patent Application No.201810796838.4 filed on Jul. 19, 2018. The contents of the aboveapplications are all incorporated by reference as if fully set forthherein in their entirety.

FIELD AND BACKGROUND OF THE INVENTION

The invention relates to a field in phosphor powder production, and inparticular to a borate fluorescent powder and a preparing methodthereof.

In the current mainstream of pursuing a low-carbon economy, white lightemitting diodes (LEDs) are highly efficient, energy-saving,environmentally friendly, and durable, and become illumination sourcesfor the new generation.

At present, fluorescent powder conversion technology is a maintechnology to realize white LEDs. There are two main methods offluorescent powder conversion technology. One is to use blue LEDs toexcite yellow fluorescent powder. Although the light conversionefficiency is high, the luminescence spectrum is mainly green andyellow, and the red is insufficient, causing low color rendering indexof the constructed white LEDs. In addition, blue light is directlyinvolved in the formation of white light, and blue light is harmful tohuman eyes. The other is to construct white LEDs by utilizing red,green, and blue fluorescent powders excited by ultraviolet ornear-ultraviolet light. The color of white LEDs by this method isstable. The red fluorescent powder is crucial to construct white LEDs,but near-ultraviolet light is weakly absorbed when a 4f-4f transitionoccurs to Eu³⁺ (positive trivalent europium ion) in conventional redfluorescent powder, causing low luminous efficiency.

In summary, when a 4f-4f transition occurs to Eu³⁺ in conventional redfluorescent powder, near-ultraviolet light is weakly absorbed, causinglow luminous efficiency. Hence, when the red fluorescent powder iscombined with the green and blue fluorescent powders to construct whiteLEDs, colors thereof are unstable, and luminous efficiency thereof islow.

SUMMARY OF THE INVENTION

The present disclosure provides a borate fluorescent powder, solving theproblem that conventional red fluorescent powder has low luminousefficiency.

In order to solve the above problem, the technical solution provided bythe present disclosure is as follows:

A method for preparing a borate fluorescent powder of a formula:Ba_(2-n)Sr_(n)Lu_(5-x-y-m-z)L_(m)Ce_(x)Tb_(y)Eu_(z)B₅O₁₇ is provided inthe present disclosure, wherein L is one or any combination of theelements Gd, La, and Sc; x, y, z, m, and n all are mole fractions; andranges of x, y, z, m, and n respectively are 0.001<x≤0.3, 0.001<y≤2,0.01<z≤0.3, 0≤m≤1, and 0≤n≤0.5, the method comprising steps of:

a step S10 of weighing stoichiometric amounts of the required rawmaterials of A, B, C, D, E, F, G, H, I, and J, and then mixing andgrounding the required raw materials to obtain a first mixture, whereinthe raw material of A is a compound including Ba²⁺, the raw material ofB is a compound including Ce³⁺, the raw material of C is a compoundincluding Tb³⁺, the raw material of D is a compound including Eu³⁺, theraw material of E is a compound including B³⁺, the raw material of F isa compound of Sr²⁺, the raw material of G is a compound including La³⁺,the raw material of H is a compound including Gd³⁺, the raw material ofI is a compound including Lu³⁺, and the raw material of J is a compoundincluding Sc³⁺;

a step S20 of performing a first heat treatment on the first mixtureunder a condition of reduction gas to obtain a second mixture; and

a step S30 of performing a second heat treatment on the second mixtureunder the condition of reduction gas, and then cooling and grinding thesecond mixture to obtain the borate fluorescent powder of formulaBa_(2-n)Sr_(n)Lu_(5-x-y-m-z)L_(m)Ce_(x)Tb_(y)Eu_(z)B₅O₁₇, wherein thereduction gas is carbon monoxide or hydrogen.

In at least an embodiment of the present disclosure, a sum of molenumbers of La³⁺ in the raw material of G, Gd³⁺ in the raw material of H,and Sc³⁺ in the raw material of J is a, a ratio of mole numbers of Ba²⁺in the raw material of A, Sr²⁺ in the raw material of F, Lu³⁺ in the rawmaterial of I, Ce³⁺ in the raw material of B, Tb³⁺ in the raw materialof C, Eu³⁺ in the raw material of D, and B³⁺ in the raw material of Ewith respect to the a isBa²⁺:Sr²⁺:Lu³⁺:Ce³⁺:Tb³⁺:Eu³⁺:B³⁺:a=(2-n):n:(5-x-y-m-z): x:y:z: 5:m.

In at least an embodiment of the present disclosure, any one of the rawmaterials of A, B, C, D, F, G, H, I, and J can only include at most oneof metal ions which are Ba²⁺, Sr²⁺, Lu³⁺, Ce³⁺, Tb³⁺, Eu³⁺, La³⁺, Gd³⁺,and Sc³⁺.

In at least an embodiment of the present disclosure, any one of the rawmaterials of A, B, C, D, F, G, H, I, and J is one or any combination ofcarbonates, nitrates, and halides.

In at least an embodiment of the present disclosure, a temperature ofthe first heat treatment ranges from 350° C. to 600° C., and a durationof the first heat treatment ranges from 1 to 6 hours.

In at least an embodiment of the present disclosure, a temperature ofthe second heat treatment ranges from 1000° C. to 1300° C., and aduration of the second heat treatment ranges from 2 to 24 hours.

A borate fluorescent powder having a formula:Ba_(2-n)Sr_(n)Lu_(5-x-y-m-z)L_(m)Ce_(x)Tb_(y)Eu_(z)B₅O₁₇ is furtherprovided in the present disclosure, wherein L is one or any combinationof the elements Gd, La, and Sc; x, y, z, m, and n are all molefractions; and ranges of x, y, z, m, and n are respectively 0<x≤0.6,0<y≤3, 0<z≤0.4, 0≤m≤1, and 0≤n≤0.5.

In at least an embodiment of the present disclosure, ranges of x, y, andz respectively are 0.001<x≤0.3, 0.001<y≤2, and 0.01<z≤0.3.

Another method for preparing a borate fluorescent powder of a formula:Ba_(2-n)Sr_(n)Lu_(5-x-y-m-z)L_(m)Ce_(x)Tb_(y)Eu_(z)B₅O₁₇ is provided inthe present disclosure, wherein L is one or any combination of theelements Gd, La, and Sc; x, y, z, m, and n all are mole fractions; andranges of x, y, z, m, and n respectively are 0<x≤0.6, 0<y≤3, 0<z≤0.4,0≤m≤1, and 0≤n≤0.5, the method comprising steps of:

a step S10 of weighing stoichiometric amounts of the required rawmaterials of A, B, C, D, E, F, G, H, I, and J, and then mixing andgrounding the required raw materials to obtain a first mixture, whereinthe raw material of A is a compound including Ba²⁺, the raw material ofB is a compound including Ce³⁺, the raw material of C is a compoundincluding Tb³⁺, the raw material of D is a compound including Eu³⁺, theraw material of E is a compound including B³⁺, the raw material of F isa compound of Sr²⁺, the raw material of G is a compound including La³⁺,the raw material of H is a compound including Gd³⁺, the raw material ofI is a compound including Lu³⁺, and the raw material of J is a compoundincluding Sc³⁺;

a step S20 of performing a first heat treatment on the first mixtureunder a condition of reduction gas to obtain a second mixture; and

a step S30 of performing a second heat treatment on the second mixtureunder the condition of reduction gas, and then cooling and grinding thesecond mixture to obtain the borate fluorescent powder of formulaBa_(2-n)Sr_(n)Lu_(5-x-y-m-z)L_(m)Ce_(x)Tb_(y)Eu_(z)B₅O₁₇.

In at least an embodiment of the present disclosure, the ranges of theraw materials of x, y, and z are respectively 0.001<x≤0.3, 0.001<y≤2,and 0.01<z≤0.3.

In at least an embodiment of the present disclosure, a sum of molenumbers of La³⁺ in the raw material of G, Gd³⁺ in the raw material of H,and Sc³⁺ in the raw material of J is a, a ratio of mole numbers of Ba²⁺in the raw material of A, Sr²⁺ in the raw material of F, Lu³⁺ in the rawmaterial of I, Ce³⁺ in the raw material of B, Tb³⁺ in the raw materialof C, Eu³⁺ in the raw material of D, and B³⁺ in the raw material of Ewith respect to the a isBa²⁺:Sr²⁺:Lu³⁺:Ce³⁺:Tb³⁺:Eu³⁺:B³⁺:a=(2-n):n:(5-x-y-m-z):x:y:z:5:m.

In at least an embodiment of the present disclosure, any one of the rawmaterials of A, B, C, D, F, G, H, I, and J can only include at most oneof metal ions which are Ba²⁺, Sr²⁺, Lu³⁺, Ce³⁺, Tb³⁺, Eu³⁺, La³⁺, Gd³⁺,and Sc³⁺.

In at least an embodiment of the present disclosure, any one of the rawmaterials of A, B, C, D, F, G, H, I, and J is one or any combination ofcarbonates, nitrates, and halides.

In at least an embodiment of the present disclosure, the reduction gasis carbon monoxide or hydrogen.

In at least an embodiment of the present disclosure, a temperature ofthe first heat treatment ranges from 350° C. to 600° C., and a durationof the first heat treatment ranges from 1 to 6 hours.

In at least an embodiment of the present disclosure, a temperature ofthe second heat treatment ranges from 1000° C. to 1300° C., and aduration of the second heat treatment ranges from 2 to 24 hours.

The present disclosure has the beneficial effects: the boratefluorescent powders co-doped with cerium, terbium and europium providedby the present disclosure have stable crystalline phase, high luminousefficiency and decent thermal stability, and may be applied toultraviolet LEDs or near-ultraviolet LEDs to construct white LEDs. Inaddition, the method for preparing a borate fluorescent powder providedby the present disclosure has the advantages of simple manufacturingprocesses, easy operation and no contamination.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the presentinvention or the technical solutions in prior arts, the followingbriefly introduces the accompanying drawings used in the embodiments.Obviously, the drawings in the following description merely show some ofthe embodiments of the present invention. As regards one of ordinaryskill in the art, other drawings can be obtained in accordance withthese accompanying drawings without making creative efforts.

FIG. 1 is a step flow chart of a preparing method in accordance with afirst embodiment of the present disclosure.

FIG. 2 is an x-ray diffraction spectrum of a fluorescent powder inaccordance with the first embodiment of the present disclosure.

FIG. 3 is an excitation spectrum diagram of a fluorescent powder inaccordance with the first embodiment of the present disclosure.

FIG. 4 is an emission spectrum diagram of a fluorescent powder inaccordance with the first embodiment of the present disclosure.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The following description of the embodiments with reference to theaccompanying drawings is used to illustrate particular embodiments ofthe present disclosure. The directional terms referred in the presentdisclosure, such as “upper”, “lower”, “front”, “back”, “left”, “right”,“inner”, “outer”, “side surface”, etc. are only directions with regardto the accompanying drawings. Therefore, the directional terms used fordescribing and illustrating the present disclosure are not intended tolimit the present disclosure.

The present disclosure aims at resolving the technical problem ofconventional red fluorescent powder. When a 4f-4f transition occurs toEu³⁺ in conventional red fluorescent powder, the near-ultraviolet lightis weakly absorbed, causing low luminous efficiency. Hence, when the redfluorescent powder is combined with the green and blue fluorescentpowders to construct white LEDs, colors thereof are unstable, andluminous efficiency thereof is low. The present disclosure resolves thedefects.

First Embodiment

As shown in FIG. 1, a formula of the fluorescent powder provided in thepresent embodiment is Ba₂Lu_(2.85)Ce_(0.05)Tb₂Eu_(0.1)B₅O₁₇. Thepreparing method thereof includes the following steps:

In Step S10, stoichiometric amounts of the required raw materials of A,B, C, D, E, F, G, H, I, and J are weighed, mixed, and ground to obtain afirst mixture.

The raw material of A is BaCO₃ (barium carbonate), the raw material of Bis CeO₂ (cerium oxide), the raw material of C is Tb₄O₇ (terbium oxide),the raw material of D is Eu₂O₃ (europium (III) oxide), the raw materialof E is H₃ BO₃ (boric acid), the raw material of F is SrCO₃ (strontiumcarbonate), the raw material of G is La₂O₃ (lanthanum oxide), the rawmaterial of H is Gd₂O₃ (gadolinium oxide), the raw material of I isLu₂O₃ (lutetium oxide), and the raw material of J is Sc₂O₃ (scandiumoxide). The purity of the BaCO₃ and SrCO₃ is 99.7% or more, the purityof the H₃BO₃ is 99.8% or more, the purity of the CeO₂, Tb₄O₇, La₂O₃,Lu₂O₃, Sc₂O₃, Gd₂O₃, and Eu₂O₃ is 99% or more.

The raw materials are formulated in accordance with the stoichiometricratio of the elements included in the formula. The molar fraction ofeach element in the formula of the present embodiment isBa:Lu:Ce:Tb:Eu:B=2:2.85:0.05:2:0.1:5.

The formula does not include elements of Sr, Gd, La, and Sc. The molarfraction ratio of the BaCO₃, Lu₂O₃, CeO₂, Tb₄O₇, Eu₂O₃, H₃BO₃ is2:1.425:0.05:0.5:0.05:5. The mass of H₃BO₃ is weighed to 0.3092 g, andother raw materials are weighed in accordance with the molar fractionratios, as shown in Table 1.

TABLE 1 Raw Material A B C D E F G H I J Formula BaCO₃ CeO₂ Tb₄O₇ Eu₂O₃H₃BO₃ SrCO₃ La₂O₃ Gd₂O₃ Lu₂O₃ Sc₂O₃ Mass/g 0.3947 0.0086 0.3738 0.01760.3092 0 0 0 0.5671 0

Then, the raw material of A, the raw material of B, the raw material ofC, the raw material of D, the raw material of E, and the raw material ofI are placed in an agate mortar for grinding, and after mixedhomogeneously, a first mixture is obtained. The first mixture is placedin a corundum crucible, and then the corundum crucible is capped.

In a step S20, a first heat treatment is performed on the first mixtureunder a condition of reduction gas to obtain a second mixture.

The step S20 includes the following steps:

In a step S201, a high temperature furnace is vacuumed, and then CO gasis filled in the furnace. The purpose of vacuuming is to prevent air andmoisture in the high temperature furnace from affecting a reaction, andthe purpose of filling CO gas is to provide a reduction condition forthe reaction, so that the reactants undergo a redox reaction with theCO.

In a Step S202, the corundum crucible is placed in the high temperaturefurnace filled with CO gas, and the first sintering is performed at 450°C. to obtain the second mixture, and the duration of the first sinteringis 4 hours.

In a step S30, a second heat treatment is performed on the secondmixture under the condition of reduction gas, and then the secondmixture is cooled and grinded to obtain the fluorescent powder offormula Ba₂Lu_(2.85)Ce_(0.05)Tb₂Eu_(0.1)B₅O₁₇.

Specifically, in the high temperature furnace, the temperature is raisedto 1200° C., and the temperature is kept constant, and the secondmixture is continuously sintered for a second time, the duration of thesecond sintering is 10 hours. After the mixture cools down naturally,appropriate grinding is performed to obtain the fluorescent powder.

The sintering is a high temperature solid phase reaction process, whichconverts a powdery material into a dense object.

Refer to FIG. 2, which is a comparison diagram of an x-ray diffractionspectrum of the fluorescent powder with an x-ray diffraction spectrum ofa standard substance in accordance with the present embodiment. Wherein,the x-ray diffraction spectrum of the fluorescent powder is located ontop of the x-ray diffraction spectrum of the standard substance. It isseen from the figure that the peak positions of the diffraction spectrum(upper panel) of the fluorescent powder prepared in this embodiment isalmost identical to the control peak positions of the diffractionspectrum (lower panel) of the standard substance. Only few heterophasesare present, and the peak shapes are sharp, indicating that the productobtained from the high temperature solid phase reaction method employedin the present embodiment has high purity.

Refer to FIG. 3, which is an excitation spectrum diagram of afluorescent powder in accordance with the preferred embodiment. It isseen from the figure that the fluorescent powder has a high luminousintensity under the excitation of excitation light of 230-380 nm.

Refer to FIG. 4, which is an emission spectrum diagram of a fluorescentpowder in accordance with the embodiment. It is seen from the figurethat the peak wavelength of the fluorescent powder is 617 nm underexcitation light of 347 nm.

In the preparing method provided by the present embodiment, under theexcitation of 230-380 nm excitation light, the red emission with themain peak at 617 nm is achieved, and the color purity is high.

Second Embodiment

A formula of the fluorescent powder provided in the present embodimentis Ba₂Lu_(4.898)Ce_(0.001)Tb_(0.001)Eu_(0.1)B₅O₁₇. The preparing methodthereof includes the following steps:

In Step S10, stoichiometric amounts of the required raw materials of A,B, C, D, E, F, G, H, I, and J are weighed, mixed and then ground toobtain a first mixture.

The raw material of A is BaCO₃ (barium carbonate), the raw material of Bis CeO₂ (cerium oxide), the raw material of C is Tb₄O₇ (terbium oxide),and the raw material of D is Eu₂O₃ (europium (III) oxide), the rawmaterial of E is H₃BO₃ (boric acid), the raw material of F is SrCO₃(strontium carbonate), the raw material of G is La₂O₃ (lanthanum oxide),the raw material of H is Gd₂O₃ (gadolinium oxide), the raw material of Iis Lu₂O₃ (lutetium oxide), and the raw material of J is Sc₂O₃ (scandiumoxide). The purity of the BaCO₃ and SrCO₃ is 99.7% or more, the purityof the H₃BO₃ is 99.8% or more, the purity of CeO₂, Tb₄O₇, La₂O₃, Lu₂O₃,Sc₂O₃, Gd₂O₃ and Eu₂O₃ is 99% or more.

The raw materials are formulated in accordance with the stoichiometricratio of the elements included in the formula. The molar fraction ofeach element in the formula of the present embodiment isBa:Lu:Ce:Tb:Eu:B=2:4.898:0.001:0.001:0.1:5. The formula does not includeelements of Sr, Gd, La and Sc. The molar fraction ratio of the BaCO₃,Lu₂O₃, CeO₂, Tb₄O₇, Eu₂O₃, H₃BO₃ is 2:2.449:0.001:0.00025:0.05:5. Themass of H₃BO₃ is weighed to 0.3092 g, and other raw materials areweighed in accordance with the molar fraction ratios, as shown in Table2.

TABLE 2 Raw Material A B C D E F G H I J Formula BaC₃ CeO₂ Tb₄O₇ Eu₂O₃H₃BO₃ SrCO₃ La₂O₃ Gd₂O₃ Lu₂O₃ Sc₂O₃ Mass/g 0.3947 0.0002 0.0002 0.01760.3092 0 0 0 0.9745 0

Then, the raw material of A, the raw material of B, the raw material ofC, the raw material of D, the raw material of E, and the raw material ofI are placed in an agate mortar for grinding, and after mixedhomogeneously, a first mixture is obtained. The first mixture is placedin a corundum crucible, and then the corundum crucible is capped.

In a step S20, a first heat treatment is performed on the first mixtureunder a condition of reduction gas to obtain a second mixture.

The step S20 includes the following steps:

In a step S201, a high temperature furnace is vacuumed, and then CO gasis filled in the furnace. The purpose of vacuuming is to prevent air andmoisture in the high temperature furnace from affecting a reaction, andthe purpose of filling CO gas is to provide a reduction condition forthe reaction, so that the reactants undergo a redox reaction with theCO.

In a Step S202, the corundum crucible is placed in the high temperaturefurnace filled with CO gas, and the first sintering is performed at 480°C. to obtain the second mixture, and the duration of the first sinteringis 4 hours.

In a step S30, a second heat treatment is performed on the secondmixture under the condition of reduction gas, and then the secondmixture is cooled and grinded to obtain the fluorescent powder offormula Ba₂Lu_(4.898)Ce_(0.001)Tb_(0.001)Eu_(0.1)B₅O₁₇.

Specifically, in the high temperature furnace, the temperature is raisedto 1200° C., and the temperature is kept constant, and the secondmixture is continuously sintered for a second time, the duration of thesecond sintering is 10 hours. After the mixture cools down naturally,appropriate grinding is performed to obtain the fluorescent powder.

The sintering is a high temperature solid phase reaction process, whichconverts a powdery material into a dense object.

The x-ray diffraction spectrum, the excitation spectrum, and theemission spectrum of the fluorescent powder of the present preferredembodiment are similar to those of the first embodiment, but theemission luminous intensity of the Ce³⁺ and Tb³⁺ in the red light regionof the present embodiment is weaker than that of the first embodiment.

Third Embodiment

A formula of the fluorescent powder provided in the present embodimentis Ba_(1.5)Sr_(0.5)Lu_(4.898)Ce_(0.001)Tb_(0.001)Eu_(0.1)B₅O₁₇. Thepreparing method thereof includes the following steps:

In Step S10, stoichiometric amounts of the required raw materials of A,B, C, D, E, F, G, H, I, and J are weighed, mixed and then ground toobtain a first mixture.

The raw material of A is BaCO₃ (barium carbonate), the raw material of Bis CeO₂ (cerium oxide), the raw material of C is Tb₄O₇ (terbium oxide),the raw material of D is Eu₂O₃ (europium (III) oxide), the raw materialof E is H₃ BO₃ (boric acid), the raw material of F is SrCO₃ (strontiumcarbonate), the raw material of G is La₂O₃ (lanthanum oxide), the rawmaterial of H is Gd₂O₃ (gadolinium oxide), the raw material of I isLu₂O₃ (lutetium oxide), and the raw material of J is Sc₂O₃ (scandiumoxide). The purity of the BaCO₃ and SrCO₃ is 99.7% or more, the purityof the H₃BO₃ is 99.8% or more, the purity of the CeO₂, Tb₄O₇, La₂O₃,Lu₂O₃, Sc₂O₃, Gd₂O₃ and Eu₂O₃ is 99% or more.

The raw materials are formulated in accordance with the stoichiometricratio of the elements included in the formula. The molar fraction ofeach element in the formula of the present embodiment isBa:Sr:Lu:Ce:Tb:Eu:B=1.5:0.5:4.898:0.001:0.001:0.1:5. The formula doesnot include elements of Gd, La and Sc. The molar fraction ratio of theBaCO₃, SrCO₃, Lu₂O₃, CeO₂, Tb₄O₇, Eu₂O₃, H₃BO₃ is1.5:0.5:2.449:0.001:0.00025:0.05:5. The mass of H₃BO₃ is weighed to0.3092 g, and other raw materials are weighed in accordance with themolar fraction ratios, as shown in Table 3.

TABLE 3 Raw Material A B C D E F G H I J Formula BaCO₃ CeO₂ Tb₄O₇ Eu₂O₃H₃BO₃ SrCO₃ La₂O₃ Gd₂O₃ Lu₂O₃ Sc₂O₃ Mass/g 0.2960 0.0002 0.0002 0.01760.3092 0.0738 0 0 0.9745 0

Then, the raw material of A, the raw material of B, the raw material ofC, the raw material of D, the raw material of E, the raw material of F,and the raw material of I are placed in an agate mortar for grinding,and after mixed and homogeneously, a first mixture is obtained. Thefirst mixture is placed in a corundum crucible, and then the corundumcrucible is capped.

In a step S20, a first heat treatment is performed on the first mixtureunder a condition of reduction gas to obtain a second mixture.

The step S20 includes the following steps:

In a step S201, a high temperature furnace is vacuumed, and then CO gasis filled in the furnace. The purpose of vacuuming is to prevent air andmoisture in the high temperature furnace from affecting a reaction, andthe purpose of filling CO gas is to provide a reduction condition forthe reaction, so that the reactants undergo a redox reaction with theCO.

In a Step S202, the corundum crucible is placed in the high temperaturefurnace filled with CO gas, and the first sintering is performed at 460°C. to obtain the second mixture, and the duration of the first sinteringis 4 hours.

In a step S30, a second heat treatment is performed on the secondmixture under the condition of reduction gas, and then the secondmixture is cooled and grinded to obtain the fluorescent powder offormula Ba_(1.5)Sr_(0.5)Lu_(4.898)Ce_(0.001)Tb_(0.001)Eu_(0.1)B₅O₁₇.

Specifically, in the high temperature furnace, the temperature is raisedto 1200° C., and the temperature is kept constant, and the secondmixture is continuously sintered for a second time, the duration of thesecond sintering is 8 hours. After the mixture cools down naturally,appropriate grinding is performed to obtain the fluorescent powder.

The sintering is a high temperature solid phase reaction process, whichconverts a powdery material into a dense object.

The x-ray diffraction spectrum, the excitation spectrum, and theemission spectrum of the fluorescent powder of the present preferredembodiment are similar to those of the first embodiment, but theemission luminous intensity of the Ce³⁺ and Tb³⁺ in the red light regionof the present embodiment is weaker than that of the first embodiment.

Forth Embodiment

A formula of the fluorescent powder provided in the present embodimentis Ba₂Lu_(1.85)La_(1.0)Ce_(0.05)Tb₂Eu_(0.1)B₅O₁₇. The preparing methodthereof includes the following steps:

In Step S10, stoichiometric amounts of the required raw materials of A,B, C, D, E, F, G, H, I, and J are weighed, mixed and then ground toobtain a first mixture.

The raw material of A is BaCO₃ (barium carbonate), the raw material of Bis CeO₂ (cerium oxide), the raw material of C is Tb₄O₇ (terbium oxide),the raw material of D is Eu₂O₃ (europium (III) oxide), the raw materialof E is H₃ BO₃ (boric acid), the raw material of F is SrCO₃ (strontiumcarbonate), the raw material of G is La₂O₃ (lanthanum oxide), the rawmaterial of H is Gd₂O₃ (gadolinium oxide), the raw material of I isLu₂O₃ (lutetium oxide), and the raw material of J is Sc₂O₃ (scandiumoxide). The purity of the BaCO₃ and SrCO₃ is 99.7% or more, the purityof the H₃BO₃ is 99.8% or more, the purity of the CeO₂, Tb₄O₇, La₂O₃,Lu₂O₃, Sc₂O₃, Gd₂O₃ and Eu₂O₃ is 99% or more.

The raw materials are formulated in accordance with the stoichiometricratio of the elements included in the formula. The molar fraction ofeach element in the formula of the present embodiment isBa:Lu:La:Ce:Tb:Eu:B=2:1.85:1.0:0.05:2:0.1:5. The formula does notinclude elements of Sr, Gd and Sc. The molar fraction ratio of theBaCO₃, Lu₂O₃, La₂O₃, CeO₂, Tb₄O₇, Eu₂O₃, H₃BO₃ is2:0.925:0.5:0.05:0.5:0.05:5. The mass of H₃BO₃ is weighed to 0.3092 g,and other raw materials are weighed in accordance with the molarfraction ratios, as shown in Table 4.

TABLE 4 Raw Material A B C D E F G H I J Formula BaCO₃ CeO₂ Tb₄O₇ Eu₂O₃H₃BO₃ SrCO₃ La₂O₃ Gd₂O₃ Lu₂O₃ Sc₂O₃ Mass/g 0.3947 0.0086 0.3738 0.01760.3092 0 0.1629 0 0.3681 0

Then, the raw material of A, the raw material of B, the raw material ofC, the raw material of D, the raw material of E, the raw material of G,and the raw material of I are placed in an agate mortar for grinding,and after mixed and homogeneously, a first mixture is obtained. Thefirst mixture is placed in a corundum crucible, and then the corundumcrucible is capped.

In a step S20, a first heat treatment is performed on the first mixtureunder a condition of reduction gas to obtain a second mixture.

The step S20 includes the following steps:

In a step S201, a high temperature furnace is vacuumed, and then CO gasis filled in the furnace. The purpose of vacuuming is to prevent air andmoisture in the high temperature furnace from affecting a reaction, andthe purpose of filling CO gas is to provide a reduction condition forthe reaction, so that the reactants undergo a redox reaction with theCO.

In a Step S202, the corundum crucible is placed in the high temperaturefurnace filled with CO gas, and the first sintering is performed at 450°C. to obtain the second mixture, and the duration of the first sinteringis 4 hours.

In a step S30, a second heat treatment is performed on the secondmixture under the condition of reduction gas, and then the secondmixture is cooled and grinded to obtain the fluorescent powder offormula Ba₂L_(1.85)La_(1.0)Ce_(0.05)Tb₂Eu_(0.1)B₅O₁₇.

Specifically, in the high temperature furnace, the temperature is raisedto 1190° C., and the temperature is kept constant, and the secondmixture is continuously sintered for a second time, the duration of thesecond sintering is 14 hours. After the mixture cools down naturally,appropriate grinding is performed to obtain the fluorescent powder.

The sintering is a high temperature solid phase reaction process, whichconverts a powdery material into a dense object.

The x-ray diffraction spectrum, the excitation spectrum, and theemission spectrum of the fluorescent powder of the present preferredembodiment are similar to those of the first embodiment, but theemission luminous intensity of the Ce³⁺ and Tb³⁺ in the red light regionof the present embodiment is weaker than that of the first embodiment.

Fifth Embodiment

A formula of the fluorescent powder provided in the present embodimentis: Ba₂Lu_(1.85)La_(1.0)Ce_(0.05)Tb₂Eu_(0.1)B₅O₁₇. The preparing methodthereof includes the following steps:

In Step S10, stoichiometric amounts of the required raw materials of A,B, C, D, E, F, G, H, I, and J are weighed, mixed and the ground toobtain a first mixture.

The raw material of A is BaCO₃ (barium carbonate), the raw material of Bis CeO₂ (cerium oxide), the raw material of C is Tb₄O₇ (terbium oxide),the raw material of D is Eu₂O₃ (europium (III) oxide), the raw materialof E is H₃ BO₃ (boric acid), the raw material of F is SrCO₃ (strontiumcarbonate), the raw material of G is La₂O₃ (lanthanum oxide), the rawmaterial of H is Gd₂O₃ (gadolinium oxide), the raw material of I isLu₂O₃ (lutetium oxide), and the raw material of J is Sc₂O₃ (scandiumoxide). The purity of the BaCO₃ and SrCO₃ is 99.7% or more, the purityof H₃BO₃ is 99.8% or more, the purity of the CeO₂, Tb₄O₇, La₂O₃, Lu₂O₃,Sc₂O₃, Gd₂O₃ and Eu₂O₃ is 99% or more.

The raw materials are formulated in accordance with the stoichiometricratio of the elements included in the formula. The molar fraction ofeach element in the formula of the present embodiment isBa:Lu:Gd:Ce:Tb:Eu:B=2:1.85:1.0:0.05:2:0.1:5. The formula does notinclude elements of Sr, La and Sc. The molar fraction ratio of theBaCO₃, Lu₂O₃, Gd₂O₃, CeO₂, Tb₄O₇, Eu₂O₃, H₃BO₃ is2:0.925:0.5:0.05:0.5:0.05:5. The mass of H₃BO₃ is weighed to 0.3092 g,and other raw materials are weighed in accordance with the molarfraction ratios, as shown in Table 5.

TABLE 5 Raw Material A B C D E F G H I J Formula BaCO₃ CeO₂ Tb₄O₇ Eu₂O₃H₃BO₃ SrCO₃ La₂O₃ Gd₂O₃ Lu₂O₃ Sc₂O₃ Mass/g 0.3947 0.0086 0.3738 0.01760.3092 0 0 0.1813 0.3681 0

Then, the raw material of A, the raw material of B, the raw material ofC, the raw material of D, the raw material of E, the raw material of H,and the raw material of I are placed in an agate mortar for grinding,and after mixed and homogeneously, a first mixture is obtained. Thefirst mixture is placed in a corundum crucible, and then the corundumcrucible is capped.

In a step S20, a first heat treatment is performed on the first mixtureunder a condition of reduction gas to obtain a second mixture.

The step S20 includes the following steps:

In a step S201, a high temperature furnace is vacuumed, and then CO gasis filled in the furnace. The purpose of vacuuming is to prevent air andmoisture in the high temperature furnace from affecting the reaction,and the purpose of filling CO gas is to provide a reduction conditionfor a reaction, so that the reactants undergo a redox reaction with theCO.

In a Step S202, the corundum crucible is placed in the high temperaturefurnace filled with CO gas, and the first sintering is performed at 450°C. to obtain the second mixture, and the duration of the first sinteringis 4 hours.

In a step S30, a second heat treatment is performed on the secondmixture under the condition of reduction gas, and then the secondmixture is cooled and grinded to obtain the fluorescent powder offormula Ba₂Lu_(1.85)La_(1.0)Ce_(0.05)Tb₂Eu_(0.1)B₅O₁₇.

Specifically, in the high temperature furnace, the temperature is raisedto 1200° C., and the temperature is kept constant, and the secondmixture is continuously sintered for a second time, the duration of thesecond sintering is 10 hours. After the mixture cools down naturally,appropriate grinding is performed to obtain the fluorescent powder.

The sintering is a high temperature solid phase reaction process, whichconverts a powdery material into a dense object.

The x-ray diffraction spectrum, the excitation spectrum, and theemission spectrum of the fluorescent powder of the present preferredembodiment are similar to those of the first embodiment, but theemission luminous intensity of the Ce³⁺ and Tb³⁺ in the red light regionof the present embodiment is weaker than that of the first embodiment.

Sixth Embodiment

A formula of the fluorescent powder is provided in the presentembodiment is Ba₂Lu_(1.35)Gd_(1.5)Ce_(0.05)Tb₂Eu_(0.1)B₅O₁₇. Thepreparing method thereof includes the following steps:

In Step S10, stoichiometric amounts of the required raw materials of A,B, C, D, E, F, G, H, I, and J are weighed, mixed and then ground toobtain a first mixture.

The raw material of A is BaCO₃ (barium carbonate), the raw material of Bis CeO₂ (cerium oxide), the raw material of C is Tb₄O₇ (terbium oxide),the raw material of D is Eu₂O₃ (europium (III) oxide), the raw materialof E is H₃BO₃ (boric acid), the raw material of F is SrCO₃ (strontiumcarbonate), the raw material of G is La₂O₃ (lanthanum oxide), the rawmaterial of H is Gd₂O₃ (gadolinium oxide), the raw material of I isLu₂O₃ (lutetium oxide), and the raw material of J is Sc₂O₃ (scandiumoxide). The purity of the BaCO₃ and SrCO₃ is 99.7% or more, the purityof the H₃BO₃ is 99.8% or more, the purity of the CeO₂, Tb₄O₇, La₂O₃,Lu₂O₃, Sc₂O₃, Gd₂O₃ and Eu₂O₃ is 99% or more.

The raw materials are formulated in accordance with the stoichiometricratio of the elements included in the formula. The molar fraction ofeach element in the formula of the present embodiment isBa:Lu:Gd:Ce:Tb:Eu:B=2:1.35:1.5:0.05:2:0.1:5. The formula does notinclude elements of Sr, La and Sc. The molar fraction ratio of theBaCO₃, Lu₂O₃, Gd₂O₃, CeO₂, Tb₄O₇, Eu₂O₃, H₃BO₃ is2:0.675:0.75:0.05:0.5:0.05:5. The mass of H₃BO₃ is weighed to 0.3092 g,and other raw materials are weighed in accordance with the molarfraction ratios, as shown in Table 6.

TABLE 6 Raw Material A B C D E F G H I J Formula BaCO₃ CeO₂ Tb₄O₇ Eu₂O₃H₃BO₃ SrCO₃ La₂O₃ Gd₂O₃ Lu₂O₃ Sc₂O₃ Mass/g 0.3947 0.0086 0.3738 0.01760.3092 0 0 0.2719 0.2687 0

Then, the raw material of A, the raw material of B, the raw material ofC, the raw material of D, the raw material of E, the raw material of H,and the raw material of I are placed in an agate mortar for grinding,and after mixed and homogeneously, a first mixture is obtained. Thefirst mixture is placed in a corundum crucible, and then the corundumcrucible is capped.

In a step S20, a first heat treatment is performed on the first mixtureunder a condition of reduction gas to obtain a second mixture.

The step S20 includes the following steps:

In a step S201, a high temperature furnace is vacuumed, and then CO gasis filled in the furnace. The purpose of vacuuming is to prevent air andmoisture in the high temperature furnace from affecting areaction, andthe purpose of filling CO gas is to provide a reduction condition forthe reaction, so that the reactants undergo a redox reaction with theCO.

In a Step S202, the corundum crucible is placed in the high temperaturefurnace filled with CO gas, and the first sintering is performed at 450°C. to obtain the second mixture, and the duration of the first sinteringis 5 hour.

In a step S30, a second heat treatment is performed on the secondmixture under the condition of reduction gas, and then the secondmixture is cooled and grinded to obtain the fluorescent powder offormula Ba₂Lu_(0.35)Gd_(1.5)Ce_(0.05)Tb₂Eu_(0.1)B₅O₁₇.

Specifically, in the high temperature furnace, the temperature is raisedto 1250° C., and the temperature is kept constant, and the secondmixture is continuously sintered for a second time, the duration of thesecond sintering is 10 hours. After the mixture cools down naturally,appropriate grinding is performed to obtain the fluorescent powder.

The sintering is a high temperature solid phase reaction process, whichconverts a powdery material into a dense object.

The x-ray diffraction spectrum, the excitation spectrum, and theemission spectrum of the fluorescent powder of the present preferredembodiment are similar to those of the first embodiment, but theemission luminous intensity of the Ce³⁺ and Tb³⁺ in the red light regionof the present embodiment is weaker than that of the first embodiment.

Seventh Embodiment

A formula of the fluorescent powder provided in the present embodimentis Ba₂Lu_(1.85)Sc_(1.0)Ce_(0.05)Tb₂Eu_(0.1)B₅O₁₇. The preparing methodthereof includes the following steps:

In Step S10, stoichiometric amounts of the required raw materials of A,B, C, D, E, F, G, H, I, and J are weighed, mixed and then ground toobtain a first mixture.

The raw material of A is BaCO₃ (barium carbonate), the raw material of Bis CeO₂ (cerium oxide), the raw material of C is Tb₄O₇ (terbium oxide),the raw material of D is Eu₂O₃ (europium (III) oxide), the raw materialof E is H₃ BO₃ (boric acid), the raw material of F is SrCO₃ (strontiumcarbonate), the raw material of G is La₂O₃ (lanthanum oxide), the rawmaterial of H is Gd₂O₃ (gadolinium oxide), the raw material of I isLu₂O₃ (lutetium oxide), and the raw material of J is Sc₂O₃ (scandiumoxide). The purity of the BaCO₃ and SrCO₃ is 99.7% or more, the purityof the H₃BO₃ is 99.8% or more, the purity of the CeO₂, Tb₄O₇, La₂O₃,Lu₂O₃, Sc₂O₃, Gd₂O₃ and Eu₂O₃ is 99% or more.

The raw materials are formulated in accordance with the stoichiometricratio of the elements included in the formula. The molar fraction ofeach element in the formula of the present embodiment isBa:Lu:Sc:Ce:Tb:Eu:B=2:1.85:1.0:0.05:2:0.1:5. The formula does notinclude elements of Sr, La and Gd. The molar fraction ratio of theBaCO₃, Lu₂O₃, Sc₂O₃, CeO₂, Tb₄O₇, Eu₂O₃, H₃BO₃ is2:0.925:0.5:0.05:0.5:0.05:5. The mass of H₃BO₃ is weighed to 0.3092 g,and other raw materials are weighed in accordance with the molarfraction ratios, as shown in Table 7.

TABLE 7 Raw Material A B C D E F G H I J Formula BaCO₃ CeO₂ Tb₄O₇ Eu₂O₃H₃BO₃ SrCO₃ La₂O₃ Gd₂O₃ Lu₂O₃ Sc₂O₃ Mass/g 0.3947 0.0086 0.3738 0.01760.3092 0 0 0 0.3681 0.0689

Then, the raw material of A, the raw material of B, the raw material ofC, the raw material of D, the raw material of E, the raw material of Iand the raw material of J are placed in an agate mortar for grinding,and after mixed homogeneously, a first mixture is obtained. The firstmixture is placed in a corundum crucible, and then the corundum crucibleis capped.

In a step S20, a first heat treatment is performed on the first mixtureunder a condition of reduction gas to obtain a second mixture.

The step S20 includes the following steps:

In a step S201, a high temperature furnace is vacuumed, and then CO gasis filled in the furnace. The purpose of vacuuming is to prevent air andmoisture in the high temperature furnace from affecting a reaction, andthe purpose of filling CO gas is to provide a reduction condition forthe reaction, so that the reactants undergo a redox reaction with theCO.

In a Step S202, the corundum crucible is placed in the high temperaturefurnace filled with CO gas, and the first sintering is performed at 450°C. to obtain the second mixture, and the duration of the first sinteringis 4 hours.

In a step S30, a second heat treatment is performed on the secondmixture under the condition of reduction gas, and then the secondmixture is cooled and grinded to obtain the fluorescent powder offormula Ba₂Lu_(1.85)Sc_(1.0)Ce_(0.05) Tb₂Eu_(0.1)B₅O₁₇.

Specifically, in the high temperature furnace, the temperature is raisedto 1200° C., and the temperature is kept constant, and the secondmixture is continuously sintered for a second time, the duration of thesecond sintering is 24 hours. After the mixture cools down naturally,appropriate grinding is performed to obtain the fluorescent powder.

The sintering is a high temperature solid phase reaction process, whichconverts a powdery material into a dense object.

The x-ray diffraction spectrum, the excitation spectrum, and theemission spectrum of the fluorescent powder of the present preferredembodiment are similar to those of the first embodiment, but theemission luminous intensity of the Ce³⁺ and Tb³⁺ in the red light regionof the present embodiment is weaker than that of the first embodiment.

Eighth Embodiment

A formula of the fluorescent powder provided in the present embodimentis Ba₂Lu₁ Ce_(0.6) Tb₃Eu_(0.4)B₅O₁₇. The preparing method thereofincludes the following steps:

In Step S10, stoichiometric amounts of the required raw materials of A,B, C, D, E, F, G, H, I, and J are weighed, mixed and then ground toobtain a first mixture.

The raw material of A is BaCO₃ (barium carbonate), the raw material of Bis CeO₂ (cerium oxide), the raw material of C is Tb₄O₇ (terbium oxide),the raw material of D is Eu₂O₃ (europium (III) oxide), the raw materialof E is H₃ BO₃ (boric acid), the raw material of F is SrCO₃ (strontiumcarbonate), the raw material of G is La₂O₃ (lanthanum oxide), the rawmaterial of H is Gd₂O₃ (gadolinium oxide), the raw material of I isLu₂O₃ (lutetium oxide), and the raw material of J is Sc₂O₃ (scandiumoxide). The purity of the BaCO₃ and SrCO₃ is 99.7% or more, the purityof the H₃BO₃ is 99.8% or more, the purity of the CeO₂, Tb₄O₇, La₂O₃,Lu₂O₃, Sc₂O₃, Gd₂O₃ and Eu₂O₃ is 99% or more.

The raw materials are formulated in accordance with the stoichiometricratio of the elements included in the formula. The molar fraction ofeach element in the formula of the present embodiment isBa:Lu:C:Tb:Eu:B=2:1:0.6:3:0.4:5. The formula does not include elementsof Sr, La and Gd. The molar fraction ratio of the BaCO₃, Lu₂O₃, CeO₂,Tb₄O₇, Eu₂O₃, H₃BO₃ is 2:0.5:0.6:0.75:0.2:5. The mass of H₃ BO₃ isweighed to 0.3092 g, and other raw materials are weighed in accordancewith the molar fraction ratios, as shown in Table 8.

TABLE 8 Raw Material A B C D E F G H I J Formula BaCO₃ CeO₂ Tb₄O₇ Eu₂O₃H₃BO₃ SrCO₃ La₂O₃ Gd₂O₃ Lu₂O₃ Sc₂O₃ Mass/g 0.3947 0.1033 0.5608 0.07040.3092 0 0 0 0.1990 0

Then, the raw material of A, the raw material of B, the raw material ofC, the raw material of D, and the raw material of I are placed in anagate mortar for grinding, and after mixed homogeneously, a firstmixture is obtained. The first mixture is placed in a corundum crucible,and then the corundum crucible is capped.

In a step S20, a first heat treatment is performed on the first mixtureunder a condition of reduction gas to obtain a second mixture.

The step S20 includes the following steps:

In a step S201, a high temperature furnace is vacuumed, and then CO gasis filled in the furnace. The purpose of vacuuming is to prevent air andmoisture in the high temperature furnace from affecting a reaction, andthe purpose of filling CO gas is to provide a reduction condition forthe reaction, so that the reactants undergo a redox reaction with theCO.

In a Step S202, the corundum crucible is placed in the high temperaturefurnace filled with CO gas, and the first sintering is performed at 500°C. to obtain the second mixture, and the duration of the first sinteringis 3 hours.

In a step S30, a second heat treatment is performed on the secondmixture under the condition of reduction gas, and then the secondmixture is cooled and grinded to obtain the fluorescent powder offormula Ba₂Lu₁Ce_(0.6)Tb₃Eu_(0.4)B₅O₁₇.

Specifically, in the high temperature furnace, the temperature is raisedto 1200° C., and the temperature is kept constant, and the secondmixture is continuously sintered for a second time, the duration of thesecond sintering is 11 hours. After the mixture cools down naturally,appropriate grinding is performed to obtain the fluorescent powder.

The sintering is a high temperature solid phase reaction process, whichconverts a powdery material into a dense object.

The x-ray diffraction spectrum, the excitation spectrum, and theemission spectrum of the fluorescent powder of the present preferredembodiment are similar to those of the first embodiment, but theemission luminous intensity of the Ce³⁺ and Tb³⁺ in the red light regionof the present embodiment is weaker than that of the first embodiment.

The beneficial effects: the borate fluorescent powder provided by thepresent disclosure has a stable crystalline phase, high luminousefficiency, and decent thermal stability, and can be applied toultraviolet LEDs or near-ultraviolet LEDs to construct white LEDs. Inaddition, the method for preparing a borate fluorescent powder providedby the present disclosure is simple in manufacturing, easy in operation,and has no contamination.

In summary, although the preferable embodiments of the presentdisclosure have been disclosed above, the embodiments are not intendedto limit the present disclosure. A person of ordinary skill in the art,without departing from the spirit and scope of the present disclosure,can make various modifications and variations. Therefore, the scope ofthe disclosure is defined in the claims.

What is claimed is:
 1. A method for preparing a borate fluorescentpowder of a formulaBa_(2-n)Sr_(n)Lu_(5-x-y-m-z)L_(m)Ce_(x)Tb_(y)Eu_(z)B₅O₁₇, wherein L isone or any combination of the elements Gd, La, and Sc; x, y, z, m, and nall are mole fractions; and ranges of x, y, z, m, and n respectively are0.001<x≤0.3, 0.001<y≤2, 0.01<z≤0.3, 0≤m≤1, and 0≤n≤0.5, the methodcomprising steps of: a step S10 of weighing stoichiometric amounts ofthe required raw materials of A, B, C, D, E, F, G, H, I, and J, and thenmixing and grinding the required raw materials to obtain a firstmixture, wherein the raw material of A is a compound including Ba²⁺, theraw material of B is a compound including Ce³⁺, the raw material of C isa compound including Tb³⁺, the raw material of D is a compound includingEu³⁺, the raw material of E is a compound including B³⁺, the rawmaterial of F is a compound of Sr²⁺, the raw material of G is a compoundincluding La³⁺, the raw material of H is a compound including Gd³⁺, theraw material of I is a compound including Lu³⁺, and the raw material ofJ is a compound including Sc³⁺; a step S20 of performing a first heattreatment on the first mixture under a condition of reduction gas toobtain a second mixture; and a step S30 of performing a second heattreatment on the second mixture under the condition of reduction gas,and then cooling and grinding the second mixture to obtain the boratefluorescent powder of formulaBa_(2-n)Sr_(n)Lu_(5-x-y-m-z)L_(m)Ce_(x)Tb_(y)Eu_(z)B₅O₁₇, wherein thereduction gas is carbon monoxide or hydrogen.
 2. The preparing method asclaimed in claim 1, wherein a sum of mole numbers of La³⁺ in the rawmaterial of G, Gd³⁺ in the raw material of H, and Sc³⁺ in the rawmaterial of J is a, a ratio of mole numbers of Ba²⁺ in the raw materialof A, Sr²⁺ in the raw material of F, Lu³⁺ in the raw material of I, Ce³⁺in the raw material of B, Tb³⁺ in the raw material of C, Eu³⁺ in the rawmaterial of D, and B³⁺ in the raw material of E with respect to the a isBa²⁺:Sr²⁺:Lu³⁺:Ce³⁺:Tb³⁺:Eu³⁺:B³⁺:a=) 2-n:(n): 5-x-y-m-z:(x:y:z: 5:m. 3.The preparing method as claimed in claim 1, wherein the raw material ofA is a compound including only one metal ion, which is Ba²⁺; the rawmaterial of B is a compound including only one metal ion, which is Ce³⁺;the raw material of C is a compound including only one metal ion, whichis Tb³⁺; the raw material of D is a compound including only one metalion, which is Eu³⁺; the raw material of F is a compound including onlyone metal ion, which is Sr²⁺; the raw material of G is a compoundincluding only one metal ion, which is La³⁺; the raw material of H is acompound including only one metal ion, which is Gd³⁺; the raw materialof I is a compound including only one metal ion, which is Lu³⁺; and theraw material of J is a compound including only one metal ion, which isSc³⁺ any one of the raw materials of A, B, C, D, F, G, H, I, and Jincludes at most one type of Ba²⁺, Sr²⁺, Lu³⁺, Ce³⁺, Tb³⁺, Eu³⁺, La³⁺,Gd³⁺, and Sc³⁺.
 4. The preparing method as claimed in claim 3, whereinany one of the raw materials of A, B, C, D, F, G, H, I, and J is one orany combination of carbonates, nitrates, and halides.
 5. The preparingmethod as claimed claim 1, wherein a temperature of the first heattreatment ranges from 350° C. to 600° C., and a duration of the firstheat treatment ranges from 1 to 6 hours.
 6. The preparing method asclaimed claim 1, wherein a temperature of the second heat treatmentranges from 1000° C. to 1300° C., and a duration of the second heattreatment ranges from 2 to 24 hours.
 7. A borate fluorescent powder,having a formula ofBa_(2-n)Sr_(n)Lu_(5-x-y-m-z)L_(m)Ce_(x)Tb_(y)Eu_(z)B₅O₁₇, wherein L isone or any combination of the elements of Gd, La, and Sc; x, y, z, m,and n are all mole fractions; and ranges of x, y, z, m, and n arerespectively 0<x≤0.6, 0<y≤3, 0<z≤0.4, 0≤m≤1, and 0≤n≤0.5.
 8. The boratefluorescent powder as claimed in claim 7, wherein ranges of x, y, and zrespectively are 0.001<x≤0.3, 0.001<y≤2, and 0.01<z≤0.3.
 9. A method forpreparing a borate fluorescent powder of a formulaBa_(2-n)Sr_(n)Lu_(5-x-y-m-z)L_(m)Ce_(x)Tb_(y)Eu_(z)B₅O₁₇, wherein L isone or any combination of the elements of Gd, La, and Sc; x, y, z, m,and n all are mole fractions; and ranges of x, y, z, m, and nrespectively are 0<x≤0.6, 0<y≤3, 0<z≤0.4, 0≤m≤1, and 0≤n≤0.5, the methodcomprising steps of: a step S10 of weighing stoichiometric amounts ofthe required raw materials of A, B, C, D, E, F, G, H, I, and J, and thenmixing and grinding the required raw materials to obtain a firstmixture, wherein the raw material of A is a compound including Ba²⁺, theraw material of B is a compound including Ce³⁺, the raw material of C isa compound including Tb³⁺, the raw material of D is a compound includingEu³⁺, the raw material of E is a compound including B³⁺, the rawmaterial of F is a compound of Sr²⁺, the raw material of G is a compoundincluding La³⁺, the raw material of H is a compound including Gd³⁺, theraw material of I is a compound including Lu³⁺, and the raw material ofJ is a compound including Sc³⁺; a step S20 of performing a first heattreatment on the first mixture under a condition of reduction gas toobtain a second mixture; and a step S30 of performing a second heattreatment on the second mixture under the condition of reduction gas,and then cooling and grinding the second mixture to obtain the boratefluorescent powder of formulaBa_(2-n)Sr_(n)Lu_(5-x-y-m-z)L_(m)Ce_(x)Tb_(y)Eu_(z)B₅O₁₇.
 10. Thepreparing method as claimed in claim 9, wherein the ranges of the rawmaterials of x, y, and z are respectively 0.001<x≤0.3, 0.001<y≤2, and0.01<z≤0.3.
 11. The preparing method as claimed in claim 9, wherein asum of mole numbers of La³⁺ in the raw material of G, Gd³⁺ in the rawmaterial of H, and Sc³⁺ in the raw material of J is a, a ratio of molenumbers of Ba²⁺ in the raw material of A, Sr²⁺ in the raw material of F,Lu³⁺ in the raw material of I, Ce³⁺ in the raw material of B, Tb³⁺ inthe raw material of C, Eu³⁺ in the raw material of D, and B³⁺ in the rawmaterial of E with respect to the a isBa²⁺:Sr²⁺:Lu³⁺:Ce³⁺:Tb³⁺:Eu³⁺:B³⁺:a=) 2-n:(n): 5-x-y-m-z:(x:y:z: 5:m.12. The preparing method as claimed in claim 9, wherein the raw materialof A is a compound including only one metal ion, which is Ba²⁺; the rawmaterial of B is a compound including only one metal ion, which is Ce³⁺;the raw material of C is a compound including only one metal ion, whichis Tb³⁺; the raw material of D is a compound including only one metalion, which is Eu³⁺; the raw material of F is a compound including onlyone metal ion, which is Sr²⁺; the raw material of G is a compoundincluding only one metal ion, which is La³⁺; the raw material of H is acompound including only one metal ion, which is Gd³⁺; the raw materialof I is a compound including only one metal ion, which is Lu³⁺; and theraw material of J is a compound including only one metal ion, which isSc³⁺ any one of the raw materials of A, B, C, D, F, G, H, I, and Jincludes at most one type of Ba²⁺, Sr²±′ Lu³⁺, Ce³⁺, Tb³⁺, Eu³⁺, La³⁺,Gd³⁺, and Sc³⁺.
 13. The preparing method as claimed in claim 12, whereinany one of the raw materials of A, B, C, D, F, G, H, I, and J is one orany combination of carbonates, nitrates, and halides.
 14. The preparingmethod as claimed in claim 9, wherein the reduction gas is carbonmonoxide or hydrogen.
 15. The preparing method as claimed claim 9,wherein a temperature of the first heat treatment ranges from 350° C. to600° C., and a duration of the first heat treatment ranges from 1 to 6hours.
 16. The preparing method as claimed claim 9, wherein atemperature of the second heat treatment ranges from 1000° C. to 1300°C., and a duration of the second heat treatment ranges from 2 to 24hours.